Trace evidence is used by forensic experts to investigate crime and accident scenes. Trace evidence can be used to indicate the direction that an investigation should take, to aid in reconstructing events, and as direct or circumstantial evidence. Thus, the proper and efficient collection and analysis of trace evidence is critical. Trace evidence may include, but is not limited to, particles large and small such as hair, paint, glass, fibers, dusts, residues, dirt, rock, as well as objects whether manmade or natural.
Tape lifting is one of the most common ways to collect trace evidence. Clear adhesive tape is selectively applied to a surface containing or potentially containing trace evidence. The evidence sticks to the tape and a clear barrier such as plastic or glass is applied to the tape to protect the evidence.
Unfortunately, tape and tape lifting have many disadvantages and problems associated with it. Tapes tend to be very sticky and therefore cannot be used on surfaces where they cannot be easily removed, such as on paper and other easily damaged or delicate surfaces. Tape will also readily collect a significant amount of non-trace evidence fibers along with trace evidence, for example unwanted clothing fibers along with trace evidence hair on the fabric. Also, tape can easily stick to itself ruining potential evidence and wasting tape. And because tape comprises a continuous adhesive sheet that sticks on a constant basis and is always exposed, contamination is possible during collection as dusts, fibers, and other matter in the air will quickly and easily stick to the tape. This remains the case even for low tack tapes that use weaker adhesives.
Thus, many things brought within proximity to the tape will stick to it, whether desirable or not. Also due to the continuous adhesive sheet the sticky side of the tape must be protected with a liner. The liner may be the plastic back of another piece of tape (as in a roll) or a separate discrete liner that is removed and discarded prior to use.
Furthermore, due to the thickness of tape, that is the combined thickness of the substrate and glue of the tape, tape does not mold well to irregularly shaped, textured, or contoured surfaces. And, because of contamination and the potentially destructive nature of tape on delicate surfaces, it cannot be indiscriminately applied to large areas. This can result in missing important trace evidence, especially on surfaces where the trace evidence easily blends in with the surface and in areas that are dark or difficult to see.
Another major problem associated with tape is the removal of the material on the tape after collection for analysis. More often than not, material cannot be simply lifted off the tape; the tape adhesive is too strong and the material will become damaged if lifting is attempted. So, solvents must be used to dissolve the adhesive and release the material. This messy procedure can damage certain type of materials. Additionally, if the trace evidence stuck to the tape displays a pattern, such as in a shoeprint, that pattern is destroyed when the solvent dissolves the adhesive.
Thus, a need presently exists for an improved trace evidence collection method.